AB0662 PERIPHERAL PLATELET-GENERATING MEGAKARYOCYTE REDUCED IN PRIMARY SJÖGREN’S SYNDROME
Authors: J. W. Hao, Y. Qiao, J. Y. Chen, J. Qiao, S. X. Zhang, X. LI, C. Wang
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Primary Sjogren’s Syndrome (pSS) is a complex and heterogeneous systemic autoimmune disease characterized by dysfunction of the secretory glands following chronic inflammation of lymphocytic infiltration.<sup>1</sup> Megakaryocytes (MKs), the precursor cells responsible for platelet production, act across the immune continuum.<sup>2</sup> However, the underlying pathogenesis of pSS involving megakaryocytes (MKs) is still to be elucidated. <h3>Objectives</h3> This study aimed to determine the changes in megakaryocyte subsets in pSS patients and to explore the role of different subsets in the pathogenesis of pSS. <h3>Methods</h3> The scRNA-seq dataset of five patients with pSS and five HCs were obtained from the GEO database to identify megakaryocytes (MKs) among PBMCs and further define the subpopulations. Then, cellular identity was determined by identifying the DEGs for each cluster using the Wilcoxon rank-sum test with the FindAllMarkers function and comparing the markers to known cell-type-specific genes from previous datasets. Finally, to investigate the hierarchy and developmental relationship between MK subpopulations, the monocle3 analysis was used to reconstruct pseudotime trajectories. <h3>Results</h3> First, four putative subpopulations (MK1-MK4) of MKs were identified by sub-clustering (Figure 1A). MK3 referred to as platelet-generating MKs, expressed key genes involved in hemostasis, cell-extracellular matrix interactions and so on. (Figure 1B) MK2 shared the same marker as MK3, but exhibited lower expression, which means MK2 may be an early stage of MK3, known as proplatelet-generating MKs. Then, compared with other MKs, MK2 and MK3 had the highest platelet activation-related and platelet aggregation-related pathways scores generated by ssGSEA (Figure 1F). Remarkably, the inflammatory response subpopulation (MK4), consisting of MKs expressing LSP11 and CD53 at high levels, was enriched in Immune system development and T-cell activation (Figure 1D). And, the proportion of the MK1, MK2, and MK4 subpopulations increased and that of the MK3 subpopulation was reduced in patients with pSS vs. HCs (Figure 1C), indicating the impaired maturation of platelet-generating MKs in pSS patients. Finally, with the trajectory analysis, we inferred that MK4 could exist independently of other MK subpopulations, and MK1 may characterize the point of initiation of a developmental trajectory (Figure 1E). <h3>Conclusion</h3> In summary, we have presented evidence for the reduction of peripheral platelet-generating MKs in patients with pSS, and identified changes in platelet-generating MKs via scRNA-seq analyses. The findings provide clues to the impaired maturation of platelet-generating MKs in the pathogenesis of pSS. <h3>References</h3> [1]RI Fox. Sjogren’s syndrome. <i>Lancet</i> 2005;366(9482):321-31. [2]LJ Noetzli, SL French, KR Machlus. New Insights Into the Differentiation of Megakaryocytes From Hematopoietic Progenitors. <i>Arterioscler Thromb Vasc Biol</i> 2019;39(7):1288-300. <h3>Disclosure of Interests</h3> None declared